A position detector called a pen tablet has been developed as one of pointing devices used for photograph processing, illustration creation, or the like, on a computer apparatus. A pen tablet is generally composed of an approximately tabular position detector portion (hereinafter referred to as a “tablet”), and a pen-like dedicated position indicator which a user manipulates on the tablet.
In one such (pen tablet) position detector based on an electromagnetic induction system, a resonance circuit is provided in a position indicator, and a reflected signal from the position indicator resonating with a signal transmitted from a tablet is detected by the tablet, to thereby obtain a position on the tablet as indicated by the position indicator (for example, refer to Japanese Patent Laid-Open No. S63-70326).
In addition, there is also proposed a position detector having a form in which a tablet is integrated with a display device such as a liquid crystal panel, whereby a position displayed on a screen is directly inputted with a position indicator such as an electronic pen (for example, refer to Japanese Patent Laid-Open No. 2002-215317).
Still further, a position detector is proposed in which a position indicator is associated with not only its specific ID information and pen pressure information, but also with other multiple types of information, of which necessary information can be selected and acquired in accordance with an instruction issued from a tablet (for example, refer to Japanese Patent Laid-Open No. H7-200137).
Yet another position detector is proposed in which a power source is provided in a position indicator to transmit a signal, and a transparent sensor tablet including a coil made of material having a high resistance, such as an ITO (Indium Tin Oxide) film, is disposed on a front surface of a liquid crystal panel (for example, refer to Japanese Patent Laid-Open No. 2007-257359).